C-12 and C-13 are stable but C-14 decays at a known rate, with a half-life of 5,568 years.University of Leicester archaeologists took four small samples from one of the ribs of the Greyfriars skeleton and sent them to two specialist units with the facilities to analyse them: the Scottish Universities Environmental Research Centre (SUERC) at the University of Glasgow, and the Oxford Radiocarbon Accelerator Unit, part of the University of Oxford’s Research Laboratory for Archaeology and the History of Art.This fact should always be remembered when using radiocarbon dates.The dating process is always designed to try to extract the carbon from a sample which is most representative of the original organism.There are two human activities recognized to have irreparably changed the global radiocarbon levels—the burning of fossil fuel and nuclear weapons testing.Radiocarbon dating is one of the most widely used scientific dating methods in archaeology and environmental science.The small pieces of bone were combusted to produce carbon dioxide which was then put through a mass spectrometer.Testing two pieces each at two different facilities should provide consistent results – and indeed it did. The proportion of C-14 in the atmosphere, and hence in living things, is not constant but varies over the centuries, and it also varies between the atmosphere and the oceans.

The carbon 14 produced reacts with oxygen atoms in the atmosphere to form carbon dioxide.In general it is always better to date a properly identified single entity (such as a cereal grain or an identified bone) rather than a mixture of unidentified organic remains.Common materials for radiocarbon dating are: The radiocarbon formed in the upper atmosphere is mostly in the form of carbon dioxide. Because the carbon present in a plant comes from the atmosphere in this way, the radio of radiocarbon to stable carbon in the plant is virtually the same as that in the atmosphere.Materials that originally came from living things, such as wood and natural fibres, can be dated by measuring the amount of carbon-14 they contain.For example, in 1991, two hikers discovered a mummified man, preserved for centuries in the ice on an alpine mountain.